Blow-out disc

ABSTRACT

A DUCTILE METAL DAMMING WASHER OR DISK, THE MARGINAL EDGE PORTION OF THE FRONT END OF WHICH IS IN CONTACT WITH A REAR ANNULAR SURFACE OF A CONSTRICTION PROVIDED WITHIN THE BARREL OF THE GUN. A SUB-CALIBRE COMBUSTION CHAMBER HAVING A SET OF RADIAL SUPPORTING MEMBERS OF KNOWN TYPE, EXTENDS THROUGH THE CONSTRICTION AND THROUGH THE DISC. THE CHAMBER IS KEPT IN A CORRECT RADIAL AND AXIAL POSITION BY MEANS OF A SECOND SET OF RADIAL SUPPORTING MEMBERS BEHIND THE DISC, SIMULTANEOUSLY CLAMPING IT TO THE CONSTRICTION. THE GAS PRESSURE, WHEN FIRING A ROUND, WILL SPLIT THE DISC AND FORM OR FOLD ITS SECTIONS INTO TAB-LIKE ELEMENTS THAT WILL EXTEND AROUND THE LEADING END OF THE SUPPORTING MEMBERS IN THE REAR SET OF SAID RADIAL SUPPORTING MEMBERS.

Oct. 26, 1971 N. E. HAGLUND ETAL 3,614,907

BLOW-OUT DISC Filed March 12, 1969 "Us EJu/Qrti United States Patent O1 fice 3,614,907 Patented Oct. 26, 1971 U.S. Cl. 891.7 4 Claims ABSTRACT OF THE DISCLOSURE A ductile metal damming washer or disk, the marginal edge portion of the front end of which is in contact with a rear annular surface of a constriction provided within the barrel of the gun. A sub-calibre combustion chamber having a set of radial supporting members of known type, extends through the constriction and through the disc. The chamber is kept in a correct radial and axial position by means of a second set of radial supporting members behind the disc, simultaneously clamping it to the constriction. The gas pressure, when firing a round, will split the disc and form or fold its sections into tab-like elements that will extend around the leading end of the supporting members in the rear set of said radial supporting members.

This application is a continuation-in-part of our copending application Ser. No. 672,573, filed Oct. 3, 1967.

The invention relates to an improved damming washer unit used in recoilless guns, for closing the rear end of the barrel.

A washer or disk of a known type is usually made of rubber, Bakelite, paper laminate or some other relatively fragile material so that the disk will break suddenly when a certain desired gas pressure is reached in the combustion chamber when launching a round. The dangerous area behind the gun is partly determined by the rather constant fire flame and the overpressure shock wave, possibly 20-30 feet for guns of this type, but portions and remnants of a conventional disk will occasionally be thrown considerably further backwards, sometimes up to 300 feet, in totally unpredictable directions. The risk of body injury is strangely enough, greater for personnel in the operating military unit, than for the gun service men.

The main object of the invention is to provide a damming unit that does not emit any splits or fragments and that can be adapted to all kinds of open recoilless guns, though preferably those having a rather long subcalibre combustion chamber. The disk itself is made of rather thin ductile metal such as aluminum alloy. It is provided with a number of weakened lines with the result that it will split into coherent fragments that will stay in the gun because they become folded over a number of supporting members located behind the disk.

In the accompanying drawing wherein an illustrative embodiment of the invention is disclosed,

FIG. 1 is a general view of the arrangement, with one half of the barrel of the gun cut away;

FIG. 2 is a longitudinal sectional view of the barrel with the combustion chamber not shown in section;

FIG. 3 is a view from the rear, looking into the Venturi of the gun, and

FIGS. 4 and 5 respectively show details of a disk fragment before and after a round has been fired.

In the gun barrel shown at 1 is arranged a sub-calibre high pressure powder charge combustion chamber 2 of known type, the rear end 13 of which has a number of centering radial supports 3. The supports 3 rest against the leading, annular shoulder or surface of a constriction section 4 provided in the rear end of the barrel, said surface forming an annular ledge or shoulder. The chamber 2 projects rearwardly somewhat beyond the constriction and into the beginning of the Venturi. The periphery of the front surface of a substantially fiat and circular disk 6 having a large center opening or hole, is passed over the chamber end 13 and is brought into contact with the trailing annular surface or ledge 5 of the constriction. A short tube 8 is fitted onto the rear of the chamber 2 behind the disk 6. The tube 8 has a number of radial supporting vanes 7. These vanes press against the rear surface of the disk 6 since the tube 8 is threaded and is urged forwardly by means of a nut 12 that is threaded onto the threaded rearmost part 12 of the chamber 2.

The tube 8, the disk 6 and the chamber 2 consequently form a unit that is firmly clampingly held in the barrel by means of the nut 12 that brings the two sets of radial supports 3 and 7 to grip firmly around the constriction 4.

The disk 6 has, as abovementioned, a center hole having substantially the same diameter as the tube 8 and it is provided with a number of radially-directed weakened lines 9 for points of fracture. The disk can also be provided with a number, preferably two, of stamped or elevated marks or ridges 10 that will lightly engage the leading edge of one of the radial supports 10. The ridges 10 are so located that the weakenings 9 will lie about midway between two adjacent vanes, thus facilitating the correct positioning of the disk when it is assembled.

The function of the disk is as follows:

When the combustion of the propelling charge starts, the gas pressure in the empty space inside of the barrel 1 will soon rise to a level where the disk will break. It is important that a breakable joint 14 between the leading end of the combustion chamber and the projectile 15 itself (not shown in the drawing) will break simultaneously or at an instant later than the disk, because otherwise a recoil or a loss in escape velocity, will result. The disk will rupture along the weakened lines 9 and its fragments or sections will form tabs 11 (FIG. 5) that will become folded around the radial supports 7 by the strong pressure exerted by the propelling gases. The folding of these tabs is shown in FIGS. 4 and 5, wherein FIG. 4 shows the position of a tab before the firing of a round and FIG. 5 shows the position of the tab thereafter.

It has been shown by tests that the fragments or tabs will in fact fold very satisfactorily even if the disk should happen to be so displaced in a rotational sense that some of the weakened lines are located very close to their corresponding radial supports.

What is claimed is:

1. A damming unit for use in a recoilless gun comprising, a barrel provided with a rear annular constriction lodging a round of ammunition, one end of the constriction receiving a breakable disk at the end of a sub-calibre combustion chamber, said chamber having a threaded end extending through the constriction, the chamber having front and rear sets of radial supports for clamping the constriction to keep the chamber in correct axial and radial position, the disk being an annular ductile metal disk arranged with its marginal edge portion in contact with a rear annular ledge provided on the constriction, the rear surface of said disk being in contact with the forward edges of the rear set of radial supports, the disk having a plurality of radial weakened lines corresponding in number to the number of radial supports in the rear set, with each radial weakened line being located in spaces between the radial supports and approximately midway between adjacent radial supports so that the disk upon the firing of a round, will separate along its lines into tab-like portions which become substantially folded into U-shape over the leading edges of the rear radial supports,

2. A damming unit according to claim 1, wherein there is provided at least two elevated ridges on the disk surface that faces the leading edges of the members of the rear set of the radial supports, said ridges engaging said leading edge thus preventing the disk from being rotationally displaced, said ridges being so located that the radial weakened lines are approximately mid-way between adjacent supporting members,

3. A damming unit for use in a recoilless gun comprising, a barrel provided with a combustion chamber located within it, the rear end of the combustion chamber being concentrically surrounded by a tube, the tube having a number of radial vanes acting to center the chamber within the barrel of the gun, the chamber having a rear threaded end, a nut threadably received on said threaded end and acting to urge the tube forwardly, a substantially fiat and circular disk composed of ductile metal, said disk being provided with a number of radially-directed weakened lines designating points of fracture for the disk so that the disk when fractured at said points will be formed With a number of tabs, the disk having a center hole through which the rear end of the combustion chamber passes, the nut being effective to force the vanes against the back surface of the disk by the tightening of said nut, a shouldered constriction in the barrel aginst which the front surface of the disk is pressed by the urging of the nut, the said disk upon the firing of a round, being divided along its weakened lines into the said tab-like portions which are substantially folded into U-shape over the leading edges of the radial supports.

4. A disk according to claim 3 having at least two elevated ridges on the disk surface facing the leading edge of the supporting vanes, said ridges engaging said leading edge, thus preventing the disk from being rotationally displaced, the ridges engaging at least one of the vanes, the ridges when being so located, causing the radial weakened lines to be disposed approximately midway between the adjacent supporting vanes.

References Cited UNITED STATES PATENTS 2,939,365 6/1960 Vaiden 89l.704 3,376,784 4/1968 Abramson 89l.703 3,380,340 4/1968 Bergman et al. 89l.703

SAMUEL W. ENGLE, Primary Examiner US. Cl. X.R. 89-l.704 

